Originally Posted by Vortex138
If they made a setting at the start of the game as to how many party members you wanted, then all the encounters would be based off of that. If you want a 4 party team, great! The CR and number of creatures you encounter would be based off of that. If you wanted 5 or 6, then the CR scale would slide based off of that.

That might be the ideal design, but a huge problem is that it would require much more play testing and balancing than designing encounters for a single maximum party size.

Each different party size would require either a change in how powerful each enemy is, or how many enemies are in the encounter. And then every permutation would need testing and balancing. That's a lot of work, if the goal is to make each party size have the same amount of challenge. Which is why most games don't do this.